This invention relates to a magnifying optical system which can be used with a determined posture of the head of a user, in which at least one of the user's eyes is directed onto an object's field, which system comprises an objective, an ocular comprising an eye lens (or eyepiece) and a deflecting (or deviating) system interposed between these.
Such a system, which is disclosed, inter alia, in German Patent Nos. 1,239,869 and 1,497,664 to Walter Zapp, is used as a telescope or magnifying glass.
Magnifying optical systems include above all the conventional microscope. However, there are applications of the latter, where it is necessary for the user to view one and the same object, with minimum possible interruptions, in continuous alternation through the microscope and immediately afterwards with the unaided eye, then again through the microscope and again with the unaided eye, and so on. The durations of viewing the object in question through the microscope and with the unaided eye are of varying length, independent of one another, and irregular.
Such alternate viewing by the observer is in particular necessary for a watchmaker in the watch industry. It is well known that a watchmaker must, completely irregularly, view the watch on which he is working sometimes through a magnifying glass and sometimes with the unaided eye if he is assembling or dismantling a watch mechanism comprising numerous small parts, for example the mechanism of a ladies' wristwatch. Frequently, the "aiding" and "restoring to normal" of the eye is effected by the watchmaker alternately manually placing in front of the eye a magnifying glass which he carries on his forehead by means of a head-band, and again manually pushing the magnifying glass away from the eye and up on the forehead.
In doing so, he must unavoidably lose sight of the precise position of the watch mechanism which he wishes to view, and must look for this position again each time he has changed his method of viewing.
A further field of use, in which "alternate viewing" by the observer, of the type described above, is necessary, is that of neuro-surgery. In brain operations and similar neuro-surgical operations, the surgeon carrying out the operation must be in the position to view a very small zone of surgery from time to time by irregular "alternate viewing" through a microscope interspersed with viewing with the unaided eye. The difficulties encountered are similar to those which confront a watchmaker when he works with a magnifying glass.